Cellulosic and starch-based Raw Materials in Ethanol Production 2. European Bioethanol Technology Meeting Detmold (Germany) April 25-26, 2006 Sven Fleischer and Thomas Senn Technology with Education and Research Distillery
Reasons for the production of bioethanol from renewable sources The production of bioethanol from renewable soucres is nearly CO 2 -neutral It s possible to substitute fossil fuels with bioethanol Bioethanol is a suitable additive for normal fuel (up to 85%)
Density of different Biomass Sources Cellulosic material [kg/m 3 ] Square bale (straw) 140 relatively low density for all kinds of cellulosic materials Square bale (whole plant) 190 Chaffed plants (whole plant) 150 Starchy material [kg/m 3 ] Cereals (corn) 760 short transport distances prefered to save energy regional distilleries prefered based on 85% dry substance Source: Handbuch Bioenergie-Kleinanlagen 2003, Kaltschmitt & Hartmann 2001
The natural structure of cellulosic materials pretreatment necessary
Methods of pretreatment for cellulosic materials Concentrated acid hydrolysis (e.g. Arkenol process) Dilute acid hydrolysis (e.g. Iogen process) Thermal hydrolysis at high temperatures (e.g. ATZ s TDH (thermal-pressure-hydrolysis)) Dispersing of the biomass and thermal hydrolysis at lower temperatures
Concentrated acid hydrolysis (e.g. the Arkenol process) 2 stage hydrolysis 1st stage 25-90% H 2 SO 4 2nd stage 20-30% H 2 SO 4 Disadvatage: corrosion of vessels possible expensive acid recycling necessary http://www.arkenol.com disposal of by-products necessary
Dilute acid hydrolysis (e.g. Iogen process) Pretreatment: acid concentrations 0,5-1% H 2 SO 4 temperatures 200-250 C (< 60 seconds) neutralisation with lime gypsum as by-product Disadvantage: accumulation of furfurals (potential inhibitors) disposal of gypsum necessary
Thermal hydrolysis - e.g. TDH (thermal-pressure-hydrolysis) ATZ Entwicklungszentrum Temperatures 180-200 C Enzymatic hydrolysis following 76% of the maximum yield from grass silage http://www.atz.de grass silage
Dispersing of the biomass and thermal hydrolysis at lower temperatures Temperatures up to 160 C No acid or other additives used Dispersing yields in dry substances of about 15% Dry substance after thermal pretreatment is about 7-8%
Comparison of the enzymatic hydrolysis of dispersed and not dispersed pretreated corn silage (whole plant) hydrolysis of carbohydrates [%] 100 90 80 70 60 50 40 30 20 10 0 160 C-30min 6,5% TS dispersed biomass 160 C-50min 5,27% TS dispersed biomass 160 C-50min 7,5%TS not dispersed biomass 155 C-25min 6,2%TS dispersed biomass 155 C-20min 6,0%TS dispersed biomass 0 20 40 60 80 100 120 140 160 48h hydrolysis duration [h] dispersing the biomass yields in faster hydrolysis after 48h about 65% of carbohydrates are hydrolysed (pretreatment at 160 C) 75% hydrolysis of carbohydrates for lower temperature of 155 C after 48h hydrolysis long hydrolysis (> 60h) is not more profitable regarding the yield of fermentable sugars
Concept of a regional ethanol production from cellulosic and starch-based materials Two different stages of biomass hydrolysis 48h enzymatical cellulase hydrolysis ratio DS cellulosic material : FS starchy material = 1:1 3 days fermentation (8%vol.) possible ethanol yield: 40l EtOH/100kg Triticale 23,6l EtOH/100kg Corn silage DS (75% hydrolysis) Triticale straw (35,4% acid soluble carbohydrates) yields in 0,28m 3 CH 4 /kg DS (= 10,08 MJ/kg DS) DS = dry substance; FS = fermentable substance
Summary Cellulosic material has a low density therefore short distances are prefered The natural structure of cellulosic biomass makes a pretreatment necessary Different strategies are used concentrated acid hydrolysis in 2 stages (e.g. Arkenol process) dilute acid hydrolysis with following enzymatic hydrolysis (e.g. Iogen process) thermal-pressure-hydrolysis (TDH) with following enzymatical hydrolysis (ATZ process) dispersing of the biomass and thermal hydrolysis at lower temperatures with following enzymatical hydrolysis
Summary dispersing the biomass combined with thermal pretreatment makes the enzymatic hydrolysis of the biomass faster dispersing the biomass combined with thermal pretreatment makes it possible to hydrolyse it up to 75% within 48h In concept of the regional ethanol production it is possible to use starch-based and cellulosic biomass in a ratio of 1:1 A 75% hydrolysis of biomass yields in 23,6 l EtOH/100 kg DS Triticale straw can be used with the thick stillage as feedstock for the biogas fermentation The Triticale straw yields in 0,28m 3 CH 4 /kg DS (= 10,08 MJ/kg DS)
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